1. Field of the Invention
The present invention relates to a method of manufacturing a long and narrow electronic part such as a thermal head which can be used for facsimile equipment, printers, plotters or the like, a print head such as an LED head, and an image sensor for reading, and a thermal head produced by this method.
2. Description of the Related Art
A long and narrow electronic part, such as a print head or an image sensor for reading, is obtained by connecting or combining a plurality of electronic parts with each other. For example, in a thermal head used for a thermal printer, a plurality of head substrates each provided with a thermal resistor are connected to each other so as to have a length which corresponds to the printing width.
In such a long and narrow electronic part, however, there is often a difference in level at joint portions, and various problems are produced. For example, in the case of a thermal head, printing is carried out by feeding paper (e.g., heat-sensitive paper) between the thermal resistor and a platen, and bringing the paper into contact with the thermal resistor. At this time, if there is a difference in level at the joints of head substrates, the contact between the thermal resistor and the paper is not uniform, thereby lowering the printing quality.
Various methods of eliminating the difference in level at the joint portions of a long and narrow electronic part have been proposed.
For example, Japanese Patent Laid-Open No. Sho 59-36474 discloses a thermal head such as that shown in FIG. 1. Head substrates 130a and 130b are fixed on support plates 131a and 131b, respectively, and the support plates 131a and 131b are fixed on a common holding base plate 132. The support plates 131a and 131b are elevated or lowered by vertically moving screws 134 driven into threaded holes 133, thereby adjusting the heights of the head substrates 130a, 130b so as to eliminate the difference in level. In order to allow such adjustment, gaps a and b are provided between the head substrate 130a and 130b, and between the support plates 131a and 131b, respectively.
In this conventional thermal head, however, since the gaps a and b are provided, if the thermal head is bent as a whole, the end portions of the head substrates 130a and 130b hit against each other and the joint is broken or chipped.
Japanese Utility Model Laid-Open No. Hei 1-175828 discloses a thermal head similar to the above-described one. In this thermal head, a slit is formed on the support plate 131 so as to allow vertical movement of the support plate 131. However, this thermal head also involves a similar problem.
Japanese Patent Laid-Open No. 60-31296 discloses a method of eliminating a difference in level at the joint between head substrates by providing a recessed portion below the joint so as to bend the head substrates when the head is pressed against the platen. This method is disadvantageous in that it is difficult to set the hardness of the platen and to select the material of the platen.